Opening device for a container and a method for producing such opening device

ABSTRACT

An opening device for a container comprises a pouring spout defining a pouring opening to pour in use the content of the container, a closing element closing the pouring opening and connected to the pouring spout by a breakable connection, and a closure fitted to the pouring spout in a removable manner to close the pouring opening at a region thereof different from that closed by the closing element; the closing element is formed in one piece with a protruding portion extending through the pouring opening and welded to the closure far away from the closing element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/107,695 filed on Jun. 23, 2016, which is a national stage ofInternational Application No. PCT/EP2014/075472 filed on Nov. 25, 2014,and claims priority to European Application No. 13199500.3 filed on Dec.23, 2013, the entire content of all three of which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to an opening device for a container, inparticular for a sealed container for packaging pourable food products,and to a method for producing such opening device.

More specifically, the present invention relates to an opening devicedesigned to be directly applied onto a sheet packaging material, in turnadapted to be folded, filled with a pourable food product and sealed toform a finished container; the present invention is also specificallydirected to a method for producing the above opening device applied ontoa multilayer sheet packaging material.

BACKGROUND DISCUSSION

As known, many pourable food products, such as fruit juice, UHT(ultra-high-temperature treated) milk, wine, tomato sauce, etc., aresold in containers made of sterilized sheet packaging material.

A typical example of this type of container is the parallelepiped-shapedcontainer for liquid or pourable food products known as Tetra BrikAseptic (registered trademark), which is made by folding and sealinglaminated strip packaging material.

The packaging material has a multilayer structure substantiallycomprising a base layer for stiffness and strength, which may comprise alayer of fibrous material, e.g. paper, or mineral-filled polypropylenematerial, and a number of lamination layers of heat-sealable plasticmaterial, e.g. polyethylene films, covering both sides of the baselayer.

In the case of aseptic containers for long-storage products, such as UHTmilk, the packaging material also comprises a layer of gas-barriermaterial, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, whichis superimposed on a layer of heat-sealable plastic material, and is inturn covered with another layer of heat-sealable plastic materialforming the inner face of the container eventually contacting the foodproduct.

Containers of this sort are normally produced on fully automaticpackaging machines, on which a continuous tube is formed from theweb-fed packaging material; the web of packaging material is sterilizedon the packaging machine, e.g. by applying a chemical sterilizing agent,such as a hydrogen peroxide solution, which, once sterilization iscompleted, is removed from the surfaces of the packaging material, e.g.evaporated by heating; the web of packaging material so sterilized isthen maintained in a closed, sterile environment, and is folded andsealed longitudinally to form a vertical tube.

The tube is filled with the sterilized or sterile-processed foodproduct, and is sealed and subsequently cut along equally spaced crosssections to form pillow packs, which are then folded mechanically toform respective finished, e.g. substantially parallelepiped-shaped,containers.

Alternatively, the packaging material may be cut into blanks, which areformed into containers on forming spindles, and the containers arefilled with the food product and sealed. One example of this type ofcontainer is the so-called “gable-top” container known by the trade nameTetra Rex (registered trademark).

To open the containers described above, various solutions have beenproposed, including reclosable opening devices made of plastic materialand substantially comprising a pouring spout, defining a through pouringopening and fitted to a hole in a wall of the container.

When producing the opening device, the opening of the pouring spout issealed by a plastic closing element connected integrally to the pouringspout and detachable from it along a smaller-section annular tearablemembrane; the closing element extends at the same level as the packagingmaterial so as to seal the hole in the wall of the container.

A removable, e.g. screw or hinged, lid can be fitted to the pouringspout to outwardly closing the latter and allowing closure of thecontainer after the first opening by removing the closing element.

An example of the above-mentioned opening device is shown inEP-A-2508432. In this case, the pouring spout and the closing elementare injection molded in one piece directly on the hole formed in thepackaging material so as to seal it.

In particular, the portion of the packaging material provided with thehole on which the pouring spout and the closing element are to be formedis placed between two molds in an open configuration. The molds are thendisplaced towards the packaging material to reach a closedconfiguration, in which they cooperate with opposite faces of thepackaging material and define a closed mold cavity housing theabove-mentioned hole. The injection molding operation is performed byinjecting the molten plastic material in the mold cavity defined by themolds in the closed configuration. More specifically, the molten plasticmaterial is forced to fill completely the mold cavity so as to form thepouring spout and the closing element.

Subsequently, a lid is fitted to the pouring spout to close the pouringopening at a region thereof different from that closed by the closingelement.

In particular, in the position closing the pouring spout, the lid has alowered end wall inserted within the pouring spout and placed in contactwith the closing element. The lid also has a conductive layer in itsbottom surface contacting the closing element.

The lid is then welded to the closing element by an induction heatingwelding operation. In greater details, an electric current is induced inthe conductive layer of the lid so as to generate a localized heatadapted to melt the plastic materials of the contacting surfaces whichthen solidify in a welded condition.

It is also specified that the conductive layer may be provided in theclosing element instead of the lid.

The described solution of opening device permits a one-step, low-effortopening of the container by simply raising the lid. During thismovement, a pulling action is exerted on the closing element secured tothe lid, which is torn from the pouring spout along the smaller-sectionannular membrane. In particular, the tearing action starts at a givenpoint of the annular membrane and then propagates to the rest of themembrane up to produce a complete detachment of the closing element fromthe pouring spout.

However, the solution disclosed in EP-A-2508432 has the drawback thatthe induction heating welding operation is performed too close to thepackaging material with some concerns as to the integrity of the latter.In particular, in order to avoid any possible damage to the packagingmaterial in the zone adjacent to the opening device, it is necessary tocontrol and to limit the pressure and the temperature reached during thewelding operation. As a matter of fact, the electromagnetic energygenerated by the induction process is partially transferred to thepackaging material in the form of heat, which may produce damages to thepackaging material itself.

Due to the temperature and pressure limitations, the time necessary toperform the welding operation is relatively high and cannot be reducedwithout increasing the risks of producing possible damages to thepackaging material or reducing the quality of the welding.

SUMMARY

Disclosed here is an opening device for a container, which is able toovercome the aforementioned drawback.

According to one aspect, a closure for an opening device of a containerincludes a lid configured to be fitted to a pouring spout of the openingdevice and welding promoting means for connecting the lid to a closingelement of the opening device. The lid comprises an end wall and acylindrical lateral wall projecting from the end wall, with thecylindrical lateral wall surrounding an interior space in the lid. Theend wall possesses an end surface facing toward the interior space ofthe lid, and the welding promoting means comprises a welding promotingelement distinct from the lid and permanently connected to the endsurface of the end wall of the lid.

In accordance with another aspect, a closure for an opening device of acontainer comprises a lid configured to be fitted to a pouring spout ofthe opening device and a welding promoting element that is weldable to aclosing element of the opening device. The lid comprises a cylindricallateral wall and an end wall completely closing one end of thecylindrical lateral wall, with the cylindrical lateral wall projectingaxially from the end wall and surrounding an interior space in the lid,and at least a portion of the cylindrical lateral wall being threaded tothreadably engage a thread on a neck of pouring spout of the container.The end wall of the lid possesses an end surface facing toward theinterior space of the lid, and the welding promoting element ispermanently fixed to the end surface of the end wall. The weldingpromoting element comprises a conductive material layer possessingopposite surfaces including one surface facing toward the end surface ofthe end wall and an other surface facing toward the interior space inthe lid, with the end wall of the lid covering an entirety of the onesurface of the conductive material layer. The other surface of theconductive material layer is covered by a heat-sealable plastic materialso that upon inducing an electric current in the conductive materiallayer the closing element may be welded to the heat-sealable plasticmaterial of the welding promoting element.

According to a further aspect, a method for producing a closure for anopening device of a container comprises; providing a lid configured tobe fitted to a pouring spout of the opening device, wherein the lidcomprises an end wall and a cylindrical lateral wall projecting from theend wall so that the cylindrical lateral wall surrounds an interiorspace in the lid. The end wall of the lid possesses an end surfacefacing toward the interior space of the lid. The method additionallyinvolves providing a welding promoting element configured to connect thelid to a closing element of the opening device, wherein the weldingpromoting element is distinct from the lid; inserting the weldingpromoting element in the lid so that the welding promoting element facesthe end surface of the end wall; and permanently connecting the weldingpromoting element to the end surface of the end wall of the lid.

BRIEF DESCRIPTION OF DRAWING FIGURES

A preferred, non-limiting embodiment of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows an axial section of an opening device according to thepresent invention, applied on a sectioned receiving portion of a sheetpackaging material forming a container;

FIG. 2 shows a larger-scale section of the FIG. 1 sheet packagingmaterial before the opening device is applied thereto;

FIG. 3 shows a smaller-scale, partly-sectioned, perspective view of theFIG. 1 opening device;

FIG. 4 shows a smaller-scale perspective view of the FIG. 1 openingdevice in an open condition;

FIG. 5 shows a smaller-scale perspective view of a closure of the FIG. 1opening device during a step for producing the closure itself;

FIG. 6 shows a larger-scale axial section of the FIG. 5 closure duringanother step for producing it;

FIG. 7 shows a perspective view of the FIG. 5 closure after itsproduction; and

FIG. 8 is analogous to FIG. 1 and shows the container provided with theopening device during a final step of the method for producing thelatter.

DETAILED DESCRIPTION

Number 1 in FIGS. 1, 3, 4 and 8 indicates as a whole a reclosableopening device for a container 100, in particular a sealed container forpackaging pourable food products.

In the example shown in FIGS. 1 and 8, opening device 1 is applied to areceiving portion 2 of a multilayer sheet packaging material 3, in turnfolded, filled with a pourable food product and sealed in a known mannerto form container 100.

With particular reference to FIG. 2, packaging material 3 comprises abase layer 4 for stiffness and strength, which may be made of fibrousmaterial, e.g. paper, or mineral-filled polypropylene material, and aplurality of layers 5 of heat-sealable plastic material, e.g.polyethylene films, covering both sides of base layer 4.

In the case of an aseptic container for long-storage products, such asUHT milk, packaging material 3 also comprises a layer 6 of gas-barriermaterial, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, whichis superimposed on a layer 5 of heat-sealable plastic material, and isin turn covered with another layer 5 of heat-sealable plastic materialforming the inner face of the container eventually contacting the foodproduct.

In other words, layers 5 and 6 define respective lamination layersapplied to base layer 4 when producing packaging material 3 in the formof a continuous strip.

In the example shown, receiving portion 2 is defined by a so-calledpre-laminated hole, i.e. a hole 9 formed through base layer 4 ofpackaging material 3 and covered by lamination layers 5, 6, so that hole9 is sealed by a sheet cover portion 10.

In a possible alternative embodiment not shown, cover portion 10 mayeven be defined by only one or some of layers 5, 6. For example, coverportion 10 may be made solely of gas-barrier material.

In another possible alternative embodiment not shown, cover portion 10may be defined by a patch fixed to the rest of packaging material 3 toseal a hole formed, in this case, through the full thickness of suchpackaging material 3.

In a further alternative embodiment not shown, receiving portion 2 maybe simply defined by a hole formed through the full thickness of thepackaging material 3 and which is destined to be sealed by openingdevice 1.

With reference to FIGS. 1, 3, 4 and 8, opening device 1 has an axis A,which in use is substantially perpendicular to receiving portion 2 ofpackaging material 3; opening device 1 basically comprises:

-   -   a pouring spout 12 fixed to packaging material 3 at hole 9 and        having a cylindrical tubular neck 13 of axis A, defining a        pouring opening 14, by which to pour in use the content of the        container;    -   a closing element 15 closing or sealing pouring opening 14 and        integrally connected to pouring spout 12 by a smaller-section,        annular membrane 16 adapted to be easily torn in use; and    -   a closure 18 fitted to neck 13 of pouring spout 12 in a        removable manner to close or seal pouring opening 14 at a region        thereof different from that closed by closing element 15.

Annular membrane 16 defines a tear line along which to detach in useclosing element 15 from pouring spout 12.

According to a preferred embodiment of the present invention, pouringspout 12 and closing element 15 are formed in one piece on receivingportion 2 of packaging material 3, whilst closure 18 is formedseparately from pouring spout 12 and closing element 15 and then fittedthereto.

In the solution disclosed in the FIGS. 1 to 4 and 8, pouring spout 12and closing element 15 are obtained by molding molten plasticmaterial—in particular by an injection molding operation—on thepackaging material 3 before it is transformed in container 100.

More specifically, the plastic material destined to form pouring spout12 and closing element 15 is injected in a molten state onto one side 10a—i.e. the side eventually facing inwards of the final container—ofcover portion 10 placed in a known manner within a molding apparatus(known per se and not shown). In particular, the molten plastic materialcovers side 10 a of cover portion 10 up to an annular peripheral regionthereof so as to form, in this way, the closing element 15 directlyattached to the cover portion 10; the molten plastic material is thenforced to pierce cover portion 10 at such annular peripheral region toform pouring spout 12 projecting from an opposite side 10 b of the coverportion 10 and attached to closing element 15 through smaller-sectionannular membrane 16, which is in turn adapted to be torn by the user toopen the container.

In this way, the material forming the pre-laminated hole is firstpierced through and then resealed by the plastic material forming thepouring spout 12.

In practice, neck 13 of pouring spout 12 extends through cover portion10 as a follow-on from the piercing thereof so as to be arranged on bothsides 10 a, 10 b of the cover portion 10 itself.

Closing element 15 and cover portion 10 of hole 9 together define asealing portion sealing pouring opening 14 of pouring spout 12. Closingelement 15 substantially has a confetti shape.

According to a possible alternative not shown, the plastic materialdestined to form pouring spout 12 and closing element 15 may be alsodirectly injected in a molten state through a hole of the packagingmaterial 3 so that such hole is then completely sealed by closingelement 15 only.

As shown particularly in FIGS. 1, 3, 4 and 8, pouring spout 12 furthercomprises an annular flange 20 fixed to packaging material 3 at the edgeof hole 9; neck 13 projects axially and integrally from an annularregion of flange 20 radially interposed between an outer edge 21 of theflange 20 itself and annular membrane 16.

In practice, closing element 15 defines a prolongation of flange 20inside pouring spout 12 and closes or seals one axial end 22 of thepouring spout 12; in a different manner, closure 18 seals the oppositeaxial end 23 of pouring spout 12, even after removal in use of closingelement 15 and cover portion 10.

Closing element 15 is advantageously formed in one piece with aprotruding portion 24 extending through pouring opening 14 and welded toclosure 18 far away from the closing element 15. In other words,protruding portion 24 is welded to closure 18 at a given, not null,axial distance from closing element 15.

With reference to FIGS. 1 and 3 to 8, closure 18 basically comprises alid 25 and a disk-shaped welding promoting element 26 to connect the lid25 to protruding portion 24.

In particular, lid 25 comprises a disk-shaped end wall 27, closingpouring opening 14 of pouring spout 12 at end 23 thereof, and acylindrical lateral wall 28 cooperating with the outer surface of neck13 of pouring spout 12.

In the example shown, lid 25 is of a screw type and lateral wall 28 hasan inner thread 29, which engages a corresponding outer thread 30 onneck 13 of pouring spout 12.

Lid 25 further comprises integrally an annular rib 27 a axiallyprotruding from end wall 27 towards the inside of the lid 25 itself anddefining a seat 27 b for receiving welding promoting element 26.

As visible in FIGS. 1, 3, 5, 6, 7 and 8, welding promoting element 26 isdefined by a multilayer sheet element 31 distinct from lid 25 andpermanently connected to the lid 25.

In particular (FIG. 3), sheet element 31 comprises a layer 32 ofconductive material, e.g. an aluminum foil, and at least two layers 33,34 of heat-sealable plastic material, e.g. polyethylene films, coveringboth sides of layer 32 and defining respective opposite faces 35, 36.

In the example shown, face 35 of sheet element 31 is configured to bewelded to end wall 27 by the heat generated by inducing an electriccurrent in layer 32; in an analogous manner, face 36 of sheet element 31is configured to be welded to protruding portion 24 by the heatgenerated by inducing an electric current in layer 32.

As shown in FIGS. 1, 3, 4 and 8, protruding portion 24 comprises anannular body 37, welded to face 36 of sheet element 31, and two legs 38integrally connecting annular body 37 to closing element 15. Inparticular, legs 38 have first ends 39, integrally connected torespective diametrically opposite portions of annular body 37 withrespect to axis A, and second ends 40 integrally connected to closingelement 15.

As a possible alternative not shown, legs 38 may be also notdiametrically opposite one another.

As a further possible alternative not shown, protruding portion 24 maycomprise more than two legs 38 angularly spaced from each other.

Opening device 1 is produced as follows.

First of all, pouring spout 12 and closing element 15 are injectionmolded in one piece onto receiving portion 2 of packaging material 3.

In particular, the packaging material 3 is placed with receiving portion2 inside a molding apparatus; at this point, the molten plastic materialis injected onto side 10 a of cover portion 10 and flows along it up tothe annular peripheral region thereof so as to form, in this way, theclosing element 15 directly attached to the cover portion 10; the moltenplastic material is then forced to pierce cover portion 10 at suchannular peripheral region to form pouring spout 12 projecting from side10 b of the cover portion 10 and attached to closing element 15 throughsmaller-section annular membrane 16. In practice, the material formingcover portion 10 is first pierced through and then resealed by theplastic material forming the pouring spout 12.

At this point, packaging material 3 is sterilized and then folded,filled with a pourable food product and sealed in a known manner toobtain container 100.

Closure 18 is produced separately from pouring spout 12 and closingelement 15 and then fitted thereto.

In particular, after forming lid 25 and sheet element 31 in knownmanner, the latter is inserted into seat 27 b of the lid 25 with face 35in contact with end wall 27. The assembly so formed is then insertedbetween a pressure element 41 and an electric induction generatingelement 42 of an induction heating welding apparatus 43. Morespecifically, in the example shown in FIG. 6, the pressure element 41also engages seat 27 b of lid 25 and cooperates with face 36 of sheetelement 31; electric induction generating element 42 comprises a coil 44and cooperates with an external surface of end wall 27 of lid 25opposite the surface of the end wall 27 itself cooperating with sheetelement 31.

By activating coil 44, an electric current is induced in layer 32 ofconductive material of sheet element 31, with a consequent generation oflocalized heat producing the welding of the face 35 of heat-sealableplastic material to end wall 27 of lid 25.

Closure 18 is then fitted to pouring spout 12 of container 100 withreciprocal engagement of threads 29 and 30.

At this point, container 100 with opening device 1 cooperates with anelectric induction generating element 46 (see FIG. 8). Morespecifically, electric induction generating element 46 is similar toelectric induction generating element 42 and comprises a coil 48;electric induction generating element 46 cooperates with the externalsurface of end wall 27 of lid 25 opposite the surface of the end wall 27itself cooperating with sheet element 31.

By activating coil 48, an electric current is induced in layer 32 ofconductive material of sheet element 31, with a consequent generation oflocalized heat producing the welding of the face 36 of heat-sealableplastic material to annular body 37 of protruding portion 24.

This induction heating welding operation is performed at a distance, nonnull, along axis A from closing element 15 and, therefore, from adjacentpackaging material 3, with no risk to damage it.

According to a possible alternative not shown, closure 18 may be fittedto pouring spout 12 and welded to protruding portion 24 of closingelement 15 by an induction heating welding operation carried outdirectly on the packaging material 3 in the form of a web, i.e. beforesuch packaging material 3 is transformed in the finished container 100.

In actual use, the first opening of the container is obtained byrotating lid 25 with respect to pouring spout 12 about axis A. At thebeginning of the rotation impressed by the user on lid 25, legs 38 bendin the direction of rotation, so exerting a pulling action on closingelement 15 at a given point of the annular membrane 16; in other words,due to the presence of the bending legs 38, the torque exerted on lid 25is transformed in a pulling action on closing element 15, which startsto detach from pouring spout 12 at two given points along annularmembrane 16.

By continuing to rotate lid 25, it unscrews completely from pouringspout 12 together with closing element 15, which remains attached to thelid 25 (see FIG. 4) and therefore fully detaches along annular membrane16 from the pouring spout 12 itself.

The advantages of the opening device 1, the closure 18 and the methodsfor producing them according to the present invention will be clear fromthe foregoing description.

In particular, thanks to the fact that closing element 15 is formed inone piece with protruding portion 24, in turn extending through pouringopening 14, the welding operation to connect the closing element 15 tolid 25 can be performed far away from the packaging material 3, withoutany risk to damage it. This also permits to have fewer constraints as tothe parameters (temperature, power, pressure, etc.) used in the weldingoperation, with possible reduction of the time necessary to perform it.

In addition, the use of a screw-type lid 25 in combination with aprotruding portion 24, including two or more legs 38 connecting sheetelement 31 to closing element 15, permits to transform the twistingaction on the lid 25 in a pulling action on the closing element 15, witha strongly reduced effort for the user with respect to similar twistingknown solutions. As a matter of fact, at the beginning of the rotationimpressed by the user on lid 25, legs 38 bend in the direction ofrotation, so producing a pulling action on closing element 15 at a givenpoint of the annular membrane 16; this causes an initial detachment ofthe closing element 15 from the pouring spout 12 at two points ofannular membrane 16 instead of requiring the same detachment along theentire annular membrane 16 simultaneously; the result is a reducedeffort experienced by the user during the initial unsealing of closure18 from pouring spout 12.

Clearly, changes may be made to opening device 1, closure 18 and themethods for producing them as described herein without, however,departing from the scope of protection as defined in the accompanyingClaims.

The invention claimed is:
 1. A closure for an opening device of acontainer, the closure comprising a lid configured to be fitted to apouring spout of the opening device, and welding promoting means forconnecting the lid to a closing element of the opening device, the lidcomprising an end wall and a cylindrical lateral wall projecting fromthe end wall, the cylindrical lateral wall surrounding an interior spacein the lid, the end wall possessing an end surface facing toward theinterior space of the lid, the welding promoting means comprise awelding promoting element distinct from the lid and permanentlyconnected to the end surface of the end wall of the lid.
 2. The closureas claimed in claim 1, wherein the cylindrical lateral wall projectingfrom the end wall of the lid possesses an inner surface facing theinterior space in the lid, the inner surface of cylindrical lateral wallincludes an interior thread that is threadably engageable with an outerthread on a neck of pouring spout of the container.
 3. The closure asclaimed in claim 1, wherein the lid includes an annular rib that isintegral with the end surface of the end wall, the annular rib extendingentirely axially towards the interior space in the lid, the annular ribsurrounding a seat at which is positioned the welding promoting element.4. The closure as claimed in claim 3, wherein the annular rib ispositioned radially inwardly of the cylindrical lateral wall so that thecylindrical lateral wall surrounds the annular rib.
 5. The closure asclaimed in claim 1, wherein the welding promoting element comprises asheet element including a layer of conductive material and having: afirst face configured to be welded to the closing element of the openingdevice by heat generated by inducing an electric current in the layer ofconductive material; and a second face opposite the first face andwelded to the end surface of the end wall of the lid of the openingdevice by heat generated by inducing an electric current in the layer ofconductive material.
 6. The closure as claimed in claim 5, wherein thesheet element further comprises a first and a second layer ofheat-sealable plastic material arranged on opposite sides of the layerof conductive material, the first layer of heat-sealable plasticmaterial defining the first face, and the second layer of heat-sealableplastic material defining the second face.
 7. The closure as claimed inclaim 5, wherein the first face of the sheet element is completelyexposed to the interior space in the lid.
 8. A closure for an openingdevice of a container, the closure comprising a lid configured to befitted to a pouring spout of the opening device and a welding promotingelement that is weldable to a closing element of the opening device, thelid comprising a cylindrical lateral wall and an end wall completelyclosing one end of the cylindrical lateral wall, the cylindrical lateralwall projecting axially from the end wall and surrounding an interiorspace in the lid, at least a portion of the cylindrical lateral wallbeing threaded to threadably engage a thread on a neck of pouring spoutof the container, the end wall of the lid possessing an end surfacefacing toward the interior space of the lid, the welding promotingelement being permanently fixed to the end surface of the end wall, thewelding promoting element comprising a conductive material layerpossessing opposite surfaces including one surface facing toward the endsurface of the end wall and an other surface facing toward the interiorspace in the lid, the end wall of the lid covering an entirety of theone surface of the conductive material layer, the other surface of theconductive material layer being covered by a heat-sealable plasticmaterial so that upon inducing an electric current in the conductivematerial layer the closing element may be welded to the heat-sealableplastic material of the welding promoting element.
 9. The closure asclaimed in claim 8, wherein the cylindrical lateral wall possesses aninner surface facing the interior space in the lid, the portion of thecylindrical lateral wall that is threaded being the inner surface of thecylindrical lateral wall.
 10. The closure as claimed in claim 9, whereinthe lid includes an annular rib that is integral with the end surface ofthe end wall, the annular rib extending entirely axially towards theinterior space in the lid, the annular rib surrounding a seat at whichis positioned the welding promoting element.
 11. The closure as claimedin claim 10, wherein the annular rib is positioned radially inwardly ofthe cylindrical lateral wall so that the cylindrical lateral wallsurrounds the annular rib.
 12. A method for producing a closure for anopening device of a container, the method comprising: providing a lidconfigured to be fitted to a pouring spout of the opening device, thelid comprising an end wall and a cylindrical lateral wall projectingfrom the end wall, the cylindrical lateral wall surrounding an interiorspace in the lid, the end wall possessing an end surface facing towardthe interior space of the lid; providing a welding promoting elementconfigured to connect the lid to a closing element of the openingdevice, the welding promoting element that is distinct from the lid;inserting the welding promoting element in the lid so that the weldingpromoting element faces the end surface of the end wall; and permanentlyconnecting the welding promoting element to the end surface of the endwall of the lid.
 13. The method as claimed in claim 12, wherein thewelding promoting element comprises a sheet element including a layer ofconductive material; and the permanently connecting of the weldingpromoting element to the end surface of the end wall of the lid isperformed by inducing an electric current in the layer of conductivematerial to produce a localized heat adapted to weld a face of the sheetelement to the end surface of the end wall of the lid.
 14. The method asclaimed in claim 12, wherein the end wall of the lid is a non-aperturedend wall so that the end wall forms a completely closed end of the lid.15. The method as claimed in claim 12, wherein the end wall of the lidto which the welding promoting element is permanently connectingincludes an annular rib axially protruding from the end wall toward theinterior space of the lid, the annular rib being positioned inwardly ofthe cylindrical lateral wall and surrounding a seat, the permanentconnection of the welding promoting element to the end surface of theend wall of the lid comprising permanently connecting the weldingpromoting element to the end surface of the end wall so that the weldingpromoting element is located at the seat.
 16. The closure as claimed inclaim 12, further comprising an annular rib axially protruding from theend wall of the lid toward the interior space of the lid, the annularrib being positioned inwardly of the cylindrical lateral wall, theannular rib surrounding a seat at which is located the welding promotingelement.
 17. The method as claimed in claim 16, wherein the end wall ofthe lid to which the welding promoting element is permanently connectingis a non-apertured end wall so that the end wall forms a completelyclosed end of the lid.